https://www.theverge.com/circuitbreaker/2018/7/19/17592138/ifixit-apple-macbook-pro-keyboard-anti-dust-membrane-update-teardown

iFixit was the first to discover that Apple’s quieter, redesigned MacBook Pro keyboards featured a membrane beneath the keycaps, which a leaked Apple repair document confirmed was to help block out unwanted dust and debris from damaging the delicate mechanism. Now, after a more thorough teardown and testing, it has confirmed that the new membrane succeeds in doing just that.

When testing the keyboard, iFixit pumped the device with a fine, powdered paint additive to see if the new membranes were merely added to cut down on the noise or if they really would block dust. As seen in the image below, the new membrane seems to be pretty effective at keeping the paint powder away from the middle part of the mechanism. iFixit notes that in a similar test, the old and membrane-less keyboard fared far worse. That said, the new keyboard still failed to protect against higher-grit particles, like sand, so you probably won’t want to bring your brand-new $6,700 MacBook Pro to the beach anytime soon.